The present invention relates to a vehicle lamp with a reflection mirror such as a tail lamp, a stop lamp and a turn signal lamp, and a method of forming the same. More particularly, the invention relates to a vehicle lamp with a reflection mirror and a method of forming the same in which an insertion hole, through which a light source is inserted into the reflection mirror of the vehicle lamp in the direction slanted to the optical axis of the reflection mirror and placed in the reflection mirror, is formed in the reflection mirror. A portion of a curved surface of the reflection mirror where the insertion hole is to be formed is smoothly continuous to the remaining portion of the curved surface without any level-difference therebetween. Multi-loop reflection steps are formed over both the portions of the curved surface, whereby the portion of the curved surface where the insertion hole is to be formed may be used as a reflection surface effective for light distribution.
A vehicle lamp is constructed such that a light source is disposed in an internal space defined by a reflection mirror and a lens, and the reflection mirror includes an insertion hole through which a bulb is inserted into the internal space of the lamp.
Usually, the bulb insertion hole is formed in the central part of the reflection mirror, and the bulb is mounted on the reflection mirror such that the center axis of the bulb is in parallel with the optical axis of the reflection mirror. In the lighting device with a bulb thus mounted, the depth of the lighting device, viz., the size thereof when measured along the optical axis of the reflection mirror, tends to increase.
For example, in the case of a rear combination lamp or the like that is mounted on the back door of an automobile, to reduce the size of the lamp mounted thereon when viewed in the longitudinal direction of the automobile, the lamp is constructed such that a bulb is inserted into the internal space of the lamp through a lamp insertion hole that is formed in the bottom of the reflection mirror.
FIGS. 16 and 17 show an example of a conventional reflection mirror a used in such a vehicle lamp.
In the reflection mirror a, a reflection surface portion d is disposed between an upper surface portion b and a bottom surface portion c, and serves as an effective reflection surface. The inner surface of the upper surface portion b and that of the bottom surface portion c are both flat, and each is a non-reflection surface.
The bottom surface portion c includes a flat portion e that is located at the middle thereof. The flat portion e is higher than another flat portion f of the bottom surface portion c. One end of the flat portion e is continuous to the reflection surface portion d, while the other end thereof is continuous with respect to a slanted portion g and the flat portion f. Accordingly, a level-difference h is present between the flat portion e and the flat portion f.
As shown in FIG. 17, a bulb insertion hole i is formed in the flat portion e. A glass bulb k of a bulb j and a part of a socket portion l thereof are disposed in front of the reflection mirror. The bulb is inserted into the inner space through the bulb insertion hole i from the lower side of the mirror.
When the bulb j is inserted into the inner space through the bulb insertion hole i and is disposed in a direction orthogonal to the optical axis of the reflection mirror a, the width of the lamp when viewed in the direction of the optical axis of the reflection mirror a may be reduced. Further, formation of the flat portion e restricts the width of the lamp when viewed in the direction orthogonal to the optical axis of the reflection mirror a.
However, in the reflection mirror thus constructed, the flat portion e is provided for forming the bulb insertion hole i. With provision of the flat portion e, the slanted portion g stands out in the light projecting direction. Thus, the slanted portion g may make a shadow to the light from the bulb j. Also, light reflected on the slanted portion g may be diffused to make a light amount distribution irregular. These problems make it difficult to effectively use the reflection surface.
With provision of the flat portion e, there is the possibility that shadows n and n (shown by slanted lines), which correspond to both sides of the slanted portion g, appear on the surface of a lens m disposed at the front of the reflection mirror a. The shadows, if they appear, mar the look of the lamp. A solution to this problem is to configure steps o formed on the lens m so as not form the shadows n and n. Another solution is to additionally use an inner lens for the same purpose.